Survivors of last month's explosion at a Titan II missile site near Damascus, Ark., have begun to question why four airmen were sent down into the silo to measure toxic vapor when an explosion was considered possible.

"They may have killed Livingston for nothing," was the way one of them put it recently referring to Senior Airmen David Livingston. Livingston was fatally injured as he emerged from the silo just as it exploded.

The Air Force accident board is investigating and its report is expected to complete next month. But interviews in Washington and Little Rock indicate conflicts already between the recollections of the participants and the official Air Force Story.

One issue is what the vice commander of the Strategic Air Command knew about the danger at the site and why he sent the young men into the silo.

Informed sources in Little Rock said that Lt. Gen. Lloyd R. Leavitte Jr. disregarded advice from experts when he ordered the men to enter the silo just before it exploded.

Throughout the evening of Sept. 18, after the volatile fuel began pouring out of the hole accidentially punched in the missile's first-stage tank and after the complex had been evacuated, experts from Martin Marietta Co. opposed any plan that involved sending airmen back into the silo area.

From the time the extent of the danger had been determined -- at about 8:30 p.m., two hours after the accident -- the Martin Marietta experts at Denver, Colo., and technicians at the Little Rock Air Force Base agreed in one of their many emergency cross-country telephone conversations with Leavitt that the possibility of an explosion was very real.

Leavitt himself recently told a Little Rock press conference that although "we never knew we were going to have [an explosion] . . . we feared it."

Shortly before the Leavitt-directed entry, the Martin Marietta experts, sources said, repeated their advice that they did not believe anyone should be allowed on or even near the missile complex for a number of hours.

At about 2 a.m., however, twin two-man entry teams and their support group of approximately 10 other airmen moved up from a safe point a quarter mile from the missile complex to a perimeter fence only 150 feet from the smoking missile silo. The entry teams had to get that close, sources here said last week, because the radios in their safety suits could transmit only that far.

When the explosion occurred at 3 a.m., one of the two airmen emerging from the silo received fatal injuries. All the other aimen who had moved up for the entry operation were among the 21 injured, some seriously.

Martin Marietta's opposition to the entry plan has not been made public up to now, although Air Force Secretary Hans Mark, in a September appearance before the House Armed Services Committee, referred to other company recommendations that the missile's fuel tank might collapse but not burst and that the silo doors should not be opened.

Air Force sources yesterday cautioned that Mark's testimony came only six days after the accident and was based on preliminary information, a point he made at the hearing. A spokesman for SAC said yesterday neither Leavitt nor any other officer would comment because the matter is under investigation.

Other portions of Mark's testimony -- to date the most complete Air Force statement on the accident -- also do not jibe with recollections of persons here in Arkansas familiar with the events.

For example, Mark described the entry plan as a "decision by people at the site to go back in" that was approved by SAC.

The airmen at the scene had in fact volunteered to go into the silo, sources said, but they had not recommended doing so and did not even know why they were being sent in to make vapor readings.

The officers and men at the site, a knowledgeable source said, "were puppets of SAC."

The Titan II missile silos are equipped with giant exhaust fans that until earlier this year were set to start automatically when deadly fuel or oxidizer vapors reached a certail level. SAC headquarters ordered the fans disconnected several months ago. That order came in the wake of an oxidizer leak last April in a silo at Potwin, Kan., where the automatic fans expelled the toxic red vapors into the air before neighboring farmers could be warned and evacuated. Headquarters directed that the fans be started only when the surrounding area was cleared of civilians.

When the fuel leak at Damascus occurred, an early proposal was to start up the fans. Ironically, according to one report, Leavitt himself turned that proposal down. Martin Marietta also opposed the reentry.

The incident began, according to published material and interviews with witnesses who requested anonymity, at about 6:30 p.m. when a maintenance man working on the upper stage of the missile dropped an eight-pound wrench socket. Because of its awkward size and weight, this particular socket had been dropped by airmen before, but it had always landed on the worker's platform and remained there. This time it rolled onto the rubber apron between the platform and the missile. Its weight pushed the rubber aside and it fell some 70 feet, bounced off a mounting at the base of the missile and ricocheted into the first-stage fuel tank. It punched a hole of three to five inches.

The fuel -- aerozine 50, highly toxic and easily ignited -- poured out, sending vapor up into the missile silo.

The maintenance crew saw the vapor rising shortly after the socket dropped, and almost immediately left the silo.

The Titan missile launch crew works out of a three-story underground, cement-reinforced shelter that is attached to the missile silo by an underground tubular walk. Separating the two are several thick blast doors, designed to prevent the shock of an explosion from passing from one to the other.

Shortly after the socket was dropped, warning devices in the crew complex showed a major fuel leak, and vapor building up in the silo. The 700-ton cement launch doors and silo exhaust ducts were closed. Thus, whatever vapors were being generated were contained within the silo. The temperatures began to rise, creating pressure within the remaining fuel and oxidizer tanks because both propellants expand when heated.

The emergency spray system went on, pouring 100,000 gallons of water down on the missile. But the spray failed to halt the leak or absorb the fuel. At that point white smoke was seen coming from the missile exhaust shaft above ground.

In less than an hour, as the missile crew watched the pressures rise, a team of specialists arrived from Little Rock Air Force Base some 50 miles away. They prepared a team in safety suits to re-enter the silo and vent -- or remove -- the vapors tha had built up from the ruptured fuel tank.

Before they could start that operation, the crew in the underground control room reported that when they opened the blast door a crack, they encountered smoke and vapor in the passageway to the silo. At the same time, one of the specialists who was on the scene warned that the first-stage fuel tank might collapse.

Shortly before 8:30 p.m., the commander of the missile crew was told by the Air Force base commander to evacuate his underground capsule. Because the passageway leading to the normal silo exit was considered dangerous, the crew left through an excape hatch, leaving all the normal entries and exits locked. When they reached the surface, they left the missile complex itself through a back gate, leaving the front gate of the complex also locked. Fifteen minutes after the order came to evacuate, the entire complex had been emptied.

At this point, two hours after the socket was dropped, the pressures recorded within the missile's fuel and oxidizer tanks were closed to the bursting point. Martin Marietta and other experts believed an explosion was possible. The word went out to evacuate all civilians within a radius of at least a half a mile from the silo. But the missilemaker's experts also maintained that although the fuel tank dome might collapse under the pressure, the rest of the tank would hold.

About 9:30 p.m., an airman entered the abandoned control center, easing himself down the exhaust shaft, and took a reading of the control panels. The fuel tank pressures were at levels near bursting. Shortly thereafter, the SAC vice commander assumed command of the accident situation from his Omaha command post and ordered that no one go on the complex again without headquarters approval.

Near midnight, Leavitt sought advice about another re-entry attempt and Martin Marietta experts said they would not permit anyone on the complex for a number of hours.

At about 2 a.m., the 15 men moved up from their staging area. As they got within 200 feet, they saw that heavy vapors covered the silo entryway.

The order from SAC headquarters was to open the locked doors, go down the three floors to the passageway between the silo and the control complex, and take fuel vapor readings.

The first two-man team had to break the lock at the gate, walk through the vapors and attempt to open the first locked blast door leading into the silo. They tried for almost 20 minutes to open the door.With oxygen running out, they returned to the perimeter gate to be placed by the second team.

While the first team was trying to open the access door, another airman walked across the complex and took a fuel vapor reading at the silo exhaust shaft. His recording device went off its scale at a dangerous 250 parts per million and he felt periodic eruptions of steam out of the vent.

The second team had better luck with the doors. They opened the first and went down the stairs to the underground passageway in the area between doors they measured 180 parts per million. When they reached the lower level between the crew complex and the silos, their recording device went off scale. They were ordered to come back up to the surface.

Just as Livingston emerged from the silo, the explosion occurred.